This invention relates to carburetors with automatic chokes and more particularly to apparatus for closing a choke valve during starting of an engine.
Carburetors with automatic chokes include a thermostatic element which holds the carburetor's choke valve closed during cold start of an engine and a vacuum motor which opens the choke valve when the engine starts. During cold start of the engine, the choke valve tends to flutter, which varies the air-fuel ratio of the mixture supplied to the engine to start it. This may lengthen the time required to start the engine, cause it to stall, and increase engine emissions during starting. When the engine is running and warms up, the closing force exerted by the thermostatic element lessens and the choke valve moves to a fully open position. After the engine is shut off, the thermostatic element gradually returns the choke valve to its closed position. When the engine is restarted after a period of shut off, the choke valve may not be fully closed but rather at some position intermediate its open and closed positions. With the choke open, an undesirably lean air-fuel mixture is supplied to the engine making it difficult to restart.